226 UPPER SANDSTONES. 



local ; nor have we a sufficient number of analogous 

 accurate observations from other parts of the world, 

 to justify any more extensive generalization. 



All that I can here pretend to do, is to give a gene- 

 ral account of those deposits which seem most uni- 

 form and extended, and which, from possessing certain 

 marked characters where they occur, have obtained 

 particular names. Those which belong to none of 

 these groups or deposits, must unavoidably be neg- 

 lected, as suited only to the topographical descriptions 

 of countries or tracts ; and it will be here sufficient 

 to remark, that they are found, not only in every part 

 of the secondary series, as inferior or subordinate mem- 

 bers of calcareous deposits, or as casual substances 

 among anomalous strata of clay, shale, and marl, but 

 among the tertiary also. The general theory of such 

 deposits has already been explained. 



After the old red sandstone, the first important one 

 is that which forms so large a portion of the coal 

 series, and the next is the red marl of England, suc- 

 ceeding to the magnesian limestone. On the Conti- 

 nent, the quadersandstein appears also to claim a rank 

 here, being separated from the red marl by the mus- 

 chelkalk ; and lastly comes the green sand, immedi- 

 ately inferior to the chalk, and above the oolithe lime- 

 stones. If the ferruginous sand of England is to be 

 distinguished from this, it must be added to the list, 

 as intermediate between the latter and the oolithes. 



The sandstones of the coal strata often extend to 

 an enormous thickness, both in the total mass and in 

 the individual beds. They are the proper repositories 

 of the coal beds with which they alternate, while they 

 also are interstratified with limestone, and with shales 

 and clays, sometimes containing nodules and beds of 

 ironstone. They are occasionally of a coarse or con- 



